Analytical Modeling of Dynamic Crack Propagation in DCB Specimens

2009 ◽  
Author(s):  
Amir Reza Shahani ◽  
Mohammad Reza Amini Fasakhodi
Keyword(s):  
Crack Propagation ◽  
Shear Deformation ◽  
Crack Growth ◽  
Crack Tip ◽  
Dynamic Crack Propagation ◽  
Velocity Versus ◽  
Beam Specimen ◽  
Dynamic Crack ◽  
Static Case ◽  
Crack Propagation Velocity

An analytical solution via the beam theory considering shear deformation effects is developed to solve the static and dynamic fracture problem in a bounded medium such as DCB (Double Cantilever Beam) specimen. In the static case, the stress intensity factor (SIF) is derived at the crack tip through the compliance approach for fixed displacement conditions. In the dynamic case, the energy balance criterion is employed to obtain the equation of motion for a running crack and the problem is solved supposing quasi-static crack propagation. Finally, a closed form relation for the crack propagation velocity versus specimen parameters and crack growth resistance of the material is found. Therefore, the effects of various parameters are investigated on the crack growth velocity. It is shown that the reacceleration of crack growth appears when the crack tip approaches the end of specimen under fixed displacement loading. The predicted results are compared with those cited in the literature and a good agreement is observed. It is seen that shear deformation effects are more significant when the small values of a0/h is considered in the analysis.

Dynamic Crack Propagation in Single-Crystalline Silicon

1998 ◽  
Vol 539 ◽  
Author(s):  
T. Cramer ◽  
A. Wanner ◽  
P. Gumbsch
Keyword(s):  
Crack Propagation ◽  
Crystalline Silicon ◽  
Potential Drop ◽  
Tensile Tests ◽  
Terminal Velocity ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Single Crystalline Silicon ◽  
Single Crystalline ◽  
Crack Propagation Velocity

AbstractTensile tests on notched plates of single-crystalline silicon were carried out at high overloads. Cracks were forced to propagate on {110} planes in a <110> direction. The dynamics of the fracture process was measured using the potential drop technique and correlated with the fracture surface morphology. Crack propagation velocity did not exceed a terminal velocity of v = 3800 m/s, which corresponds to 83%7 of the Rayleigh wave velocity vR. Specimens fractured at low stresses exhibited crystallographic cleavage whereas a transition from mirror-like smooth regions to rougher hackle zones was observed in case of the specimens fractured at high stresses. Inspection of the mirror zone at high magnification revealed a deviation of the {110} plane onto {111} crystallographic facets.

Dynamic Crack Propagation and Arrest in PWR Pressure Vessel Steel: Interpretation of Experiment With the X-FEM Method

2007 ◽  
Author(s):  
B. Prabel ◽  
S. Marie ◽  
A. Combescure
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Rate ◽  
Thermal Shock ◽  
Crack Growth ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Pressure Vessel Steel ◽  
Vessel Steel

In the frame of analysis of the pressure thermal shock in a PWR RVP and the associated R&D activities, some developments are performed at CEA on the dynamic brittle propagation and crack arrest. This paper presents a PhD work on the modeling of the dynamic brittle crack growth. For the analyses, an important experimental work is performed on different geometries using a French RPV ferritic steel: Compact Tension specimens with different thickness, isothermal rings under compression with different positions of the initial defect to study a mixed mode configuration, and a ring submitted to thermal shock. The first part of this paper details the test conditions and main results. To propose an accurate interpretation of the crack growth, a viscous-elastic-plastic dynamic model is used. The strain rate influence is taken into account based on Cowper-Symond’s law (characterization was made from Split Hopkinson Pressure Bar tests). To model the crack propagation in the Finite Element calculation, eXtended Finite Element Method (X-FEM) is used. The implementation of these specific elements in the CEA F.E. software CAST3M is described in the second part of this paper. This numerical technique avoids re-meshing, because the crack progress is directly incorporated in the degrees of freedom of the elements crossed by the crack. The last part of this paper compares the F.E. predictions to the experimental measurements using different criteria. In particular, we focused on a RKR (Ritchie-Knott-Rice) like criterion using a critical principal stress in the front of the crack tip during the dynamic crack extension. Critical stress is found to depend on crack speed, or equivalently on strain rate. Good results are reported concerning predictive simulations.

scholarly journals New experimental techniques for dynamic crack localization

2009 ◽  
pp. 255-283
Author(s):  
David Grégoire ◽  
Hubert Maigre ◽  
Fabrice Morestin
Keyword(s):  
Crack Propagation ◽  
Crack Tip ◽  
Image Correlation ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Displacement Sensors ◽  
Optical Displacement ◽  
Propagation Parameters ◽  
Tip Position

The determination of relevant constitutive crack propagation laws under dynamic loading is a rather challenging operation. In dynamic impact cases, the variations of propagation parameters and exact crack positions are difficult to control. This paper focuses on different techniques for measuring accurate crack tip position histories in dynamic crack propagation experiments. Two different methods are considered: very accurate crack tip localization by optical displacement sensors is first described for transparent materials; then, an automatic method based on digital image correlation is presented for crack localization in all brittle materials whatever their opacity.

Crack-tip parameters and temperature rise in dynamic crack propagation

1986 ◽  
Vol 23 (1) ◽  
pp. 167-182 ◽  
Author(s):  
S.N. Atluri ◽  
M. Nakagaki ◽  
T. Nishioka ◽  
Z.-B. Kuang
Keyword(s):  
Crack Propagation ◽  
Temperature Rise ◽  
Crack Tip ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack

Time dependent crack tip enrichment for dynamic crack propagation

2009 ◽  
Vol 162 (1-2) ◽  
pp. 33-49 ◽  
Author(s):  
Thomas Menouillard ◽  
Jeong-Hoon Song ◽  
Qinglin Duan ◽  
Ted Belytschko
Keyword(s):  
Crack Propagation ◽  
Crack Tip ◽  
Time Dependent ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack

scholarly journals Dynamic Fracture Toughness of a Unidirectional Graphite/Epoxy Composite

2001 ◽  
Author(s):  
C. Liu ◽  
A. J. Rosakis ◽  
M. G. Stout
Keyword(s):  
Fracture Toughness ◽  
Composite Material ◽  
Crack Propagation ◽  
Epoxy Composite ◽  
Crack Tip ◽  
Dynamic Crack Propagation ◽  
Mode I ◽  
Dynamic Crack ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness

Abstract In this investigation, we studied the process of dynamic crack propagation in a fiber-reinforced composite material using the optical Coherent Gradient Sensing (CGS) technique combined with high-speed photography. The mode-I fracture toughness of the unidirectional graphite/epoxy composite, IM7/8551-7, as a function of the crack-tip speed, was measured quantitatively. It was found that up to the Rayleigh wave speed of the composite material, the mode-I fracture toughness is a decreasing function of the crack-tip velocity. This behavior is similar to that observed in the dynamic crack propagation along interfaces between two homogeneous solids.

Molecular-Dynamics Simulations Of Fracture: An Overview Of System Size And Other Effects

1995 ◽  
Vol 409 ◽  
Author(s):  
B. L. Holian ◽  
S.J. Zhou ◽  
P.S. Lomdahl ◽  
N. Gronbech-Jensen ◽  
D.M. Beazley ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Crack Propagation ◽  
Large Scale ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Crack Tip ◽  
System Size ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Dislocation Loops

AbstractWe have studied brittle and ductile behavior and their dependence on system size and interaction potentials, using molecular-dynamics (MD) simulations. By carefully embedding a single sharp crack in two- and three-dimensional crystals, and using a variant of the efficient sound-absorbing reservoir of Holian and Ravelo [Phys. Rev. B 51, 11275 (1995)], we have been able to probe both the static and dynamic crack regimes. Our treatment of boundary and initial conditions allows us to elucidate early crack propagation mechanisms under delicate overloading, all the way up to the more extreme dynamic crack-propagation regime, for much longer times than has been possible heretofore (before unwanted boundary effects predominate). For example, we have used graphical display of atomic velocities, forces, and potential energies to expose the presence of localized phonon-like modes near the moving crack tip, just prior to dislocation emission and crack-branching events. We find that our careful MD method is able to reproduce the ZCT brittle-ductile criterion for short-range pair potentials [static lattice Green's function calculations of Zhou, Carlsson, and Thomson, Phys. Rev. Letters 72, 852 (1994)].We report on progress we have made in large-scale 3D simulations in samples that are thick enough to display realistic behavior at the crack tip, including emission of dislocation loops. Such. calculations, using our careful treatment of boundary and initial conditions - especially important in 3D - have the promise of opening up new vistas in fracture research.

Theoretical Research on the Dynamic Crack Propagation Velocity Based on Nonlocal Field Theories

2009 ◽  
Vol 417-418 ◽  
pp. 953-956
Author(s):  
Cai Ping Liu ◽  
Qing Quan Duan ◽  
Jian Ping Zuo
Keyword(s):  
Crack Propagation ◽  
Dynamic Fracture ◽  
Propagation Velocity ◽  
Characteristic Length ◽  
Theoretical Research ◽  
Field Theories ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Crack Propagation Velocity ◽  
Nonlocal Field

The purpose of this paper is to discuss the nonlocal effect on dynamic crack propagation velocity. Some experimental phenomena in dynamic fracture and simulative results using molecular & atom dynamics were analyzed and discussed in this paper. The authors found that there were still some disagreements on the dynamic crack propagation velocity. Based on these researches, we introduced nonlocal field theories into the estimation of dynamic crack propagation velocity. The dynamic crack propagation velocity is affected not only by the crack instability, but by characteristic length of material. A nonlocal characteristic length parameter M is defined through a double pile-up dislocation model. According to the Mott’s research method for crack velocity in dynamic fracture and the nonlocal field theories, an approximate theoretical dynamic propagation velocity is obtained. And we conclude that the velocity is related to the combined activity of the nonlocal characteristic length parameter M, the velocity of longitudinal wave, constant k, crack length and Poisson’s ratio.

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